Skin Cancer Myths and Facts 1-4

Myth: Self-tanner helps shield my skin from the sun.

Truth: Self-tanners do nothing more than stain the skin's top layer a bronze hue. In fact, a German study showed that self-tanners increase sun damage. If you expose yourself to the rays an hour or so after applying tanner, your skin may produce 180 percent more free radicals (unstable molecules that damage cells, potentially leading to skin cancer) than it would have had you not used the product, the study showed. This effect gradually lessens, so self-tan before bed. When you head out in the sun the next day and every day, wear a broad-spectrum sunscreen, like Banana Boat Sport Performance Lotion SPF 100 ($12.99, drugstores).

Myth: I shouldn't put sunscreen too close to my eyes.

Truth: Despite the small surface area involved, 5 to 10 percent of all skin cancers appear on eyelids. While most of these cancers are of the less deadly varieties (squamous and basal cell carcinomas), they're still a concern. "They can grow large and be very destructive," says Jordana Gilman, MD, a dermatologist in New York City. If the thought of rubbing SPF on your lids makes your eyes water, try one of the specially formulated products for sensitive skin, such as Coppertone Sensitive Skin Faces Sunscreen Lotion SPF 50 for Faces ($7.99, drugstores). Also look for sunglasses that offer 99 to 100 percent UV protection.

Myth: Sunscreens make me sweat more, especially when I work out.

Truth: Actually, researchers from Oregon State University in Corvallis found that SPF temporarily cooled their subjects' skin as they exercised. "The sun's rays are intercepted by the sunscreen's chemicals, and instead of penetrating the skin, they undergo a chemical reaction, releasing heat back into the air," explains Ellen Marmur, MD, a dermatologic surgeon in New York City. "The effect is similar to when you stop running and feel chilly because of the sweat evaporating." If your sunscreen stifles you, try another consistency. Waterproof formulas are more adhesive, but they can feel tacky, Dr. Marmur says. As an alternative, try sunscreen sticks, which won't run when you do, thanks to their waxy formula. Or use a sheer sunscreen and reapply it after you sweat. A light one: La Roche-Posay Anthelios 45 Ultra Light Sunscreen Fluid for Face ($27.90, laroche-posay.us).

Myth: I used to bake in the sun; the damage is already done.

Truth: Even if you have a "sunny" past, it's not too late to help curb your cancer risk. The notion that 80 percent of our total UV exposure occurs before age 18 was the result of misinterpreted research from the 1980s. A whopping 47 percent occurs between ages 19 and 40, according to the Skin Cancer Foundation. Not only can you help stop your accumulation today by generously applying sunblock, but you may also be able to help lessen the effects of past sun sins by doing so. A study in the New England Journal of Medicine showed that people who used sunscreen daily saw a reduction in the number of new precancerous sun spots and a slowing of the development of preexisting ones. A broad-spectrum defender we like: Aveeno Positively Ageless Sunblock Lotion SPF 70 for Face ($12.99, drugstores).

Skin Cancer Myths 5-8

Myth: I need to soak up a little sun or I'll be vitamin D deficient.

Truth: About a third of Americans worry that using sunblock daily will keep them from getting enough D, according to a Neutrogena survey. Sunscreen does cut the production of D by blocking the UV rays that skin cells use to synthesize it, but only a little sun exposure is needed to get the necessary amount of rays. After too much exposure, UV begins to break down the vitamin D created in the skin. "Too much UV is counterproductive to vitamin D synthesis," explains Linda K. Franks, MD, a dermatologist in New York City. The vitamin is crucial for bone strength and helps protect against certain cancers, diabetes, and other diseases, so doctors recommend 1,000 IU of it daily. Eat foods high in D, such as salmon, eggs, and fortified milk, and talk to your doc about taking a vitamin D3 supplement.

Myth: A little sun binge while I'm on vacation isn't so bad.

Truth: When you're kayaking in the Caribbean, it's easy to forget to reapply sunscreen, but a tan makes a risky souvenir. Women who vacationed intermittently in hot locations had 74 percent more moles, a risk factor for melanoma, than those who did not, a study in the Journal of Investigative Dermatology found. You don't have to turn lobster red to be at risk; any color is a sign that UV rays have affected your skin's DNA. And what you think is a tan may not be one at all. "If you press your skin and rosiness appears, that's a burn, even though it may not hurt," says Jennifer Linder, MD, a dermatologist in Scottsdale, Arizona. Stay safe by using an SPF wipe, such as Dr. Dennis Gross Skincare Powerful Sun Protection SPF 30 Towelettes ($18 for 20; dgskincare.com), every two hours and after sweating, toweling off, or swimming.

Myth: Spritzing on UV-protective hair mist guards my hair and scalp.

Truth: SPF hair sprays work in theory, but in practice it's difficult to coat every strand — let alone all those square inches of scalp underneath — with one. "Skin cancer can appear there and is often missed because it's hard to see beneath the hair," explains Doris Day, MD, a dermatologist in New York City. While your tresses are a type of natural sun-protective barrier, they offer a less-than-foolproof shield. "Thick hair protects better than thinner hair, and darker hair protects better than lighter," Dr. Day says. Your part, of course, is almost always fully exposed. Swipe it with a sunscreen stick, like Clinique Sun SPF 45 Targeted Protection Stick ($17.50, clinique.com). To protect your whole head, wear a tightly woven hat with a brim that's at least three inches wide.

Myth: A sunscreen with SPF 100 offers twice the protection of one with SPF 50.

Truth: The basic rules of math don't apply to SPF numbers. Here's the deal: If applied correctly, SPF 15 blocks 93 percent of UVB rays, SPF 30 stops about 97 percent and SPF 50 obstructs 98 percent. Go any higher and there's a barely detectable increase in the level of protection. (In fact, the U.S. Food and Drug Administration has proposed new labeling rules that cap SPF at 50+.) While there's no harm in using SPF 100, don't let ultrahigh numbers fool you into thinking you can apply less of it. The benefit of SPF decreases exponentially when you don't use enough, so you may end up wearing the equivalent of SPF 4 despite your bottle's triple-digit claim. Always use a one-ounce shot glass's worth of sunscreen to cover your body and a nickel-size amount to protect your face. And reapply every one to two hours.